This apparently is my own special hell when it comes to M-B ownership.

I have posted this on a couple forums in the hopes I can tap as many brains as possible. I had a similar issue with my late SL some years ago. It's now the turn of my 1991 350SD to frustrate the crap out of me.

I'm in the brake bleeding Twilight Zone.

Brakes were working ok, but needed to replace front pads. Replaced and bled rears last year, no problems. Front pistons needed to be freed up, so took care of that. After bleeding, blew the front to rear hard line. Replaced with new OEM line I had on hand, and now I can't get any fluid to the rear- nothing.

I encountered virtually the same scenario on my '88 SL years ago. At that time, I replaced the ABS unit (which was suspect) and still no fluid. I was only able to resolve this by taking the car to the dealer, where they tied into their computers and "mapped" the system. Whatever that process was, it worked and I had brakes. I have read every damned opinion there is about this, and am just hoping there might be something definitive out there as to how to get the fluid flowing again in this previously functional hydraulic system. I'm really not an idiot, and have bled brakes on many other vehicles, never having encountered a problem.

Thanks!

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Chief

1991 350SD

search for "power bleeder"
motive sells one that's perfect for the MB brakes. I've also built one from a garden sprayer.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

In many cases, I have to activate the ABS pump to properly bleed the system.

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Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership

And how did you activate it? simply with the key to "On"?

Thanks

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Chief

1991 350SD

try bleeding the master cylinder where the rear brake line enters, easy way to determine whether you have pressure or not, and once you have pressure and brake fluid move on to the rear calipers

also had luck with leaving a bleeder valve open until you get brake fluid, need to push the pedal slowly and wait between pumps


..

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1989 300ce smoke silver / brazil, in a constant state of flux ~~~

One one car I made a fused jumper wire with a switch. On later cars, I can activate the ABS pump with a scan/service tool.

Have you read the bleed procedure for this car from the service manual????

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Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership

The Bosch ABS2E used on the W126 doesn't require a special bleeding procedure.

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Which is why this is so frustrating! I've never had issues bleeding brakes BUT for my abs equipped M-B's.

In a bit of a crunch car wise, so I brought it to a garage that has pressure bleeding equipment suitable for my car. We'll see...

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Chief

1991 350SD

Try removing the bleed screw entirely. There might be rust blocking the opening. Next try disconnecting the tube from the caliper and see if anything flows. In classic cars, some people bleed the system using just gravity, not even pumping the MC. I don't know all the quirks of ABS cars.

To make sure the rear rubber in the master cylinder is clearing the fluid port when the pedal is up. Add some brake fluid making sure the right part of the master cylinder plastic container is really full.

Remove the bleeder screw and watch. Gravity should get fluid out back there with a little time. If the fluid does not show up there is a chance the rubber in the master cylinder is not working properly. Still blocking off the fill port when it should not. Anyways a gravity bleed should work okay on that model . Elevating the front end should speed it up a little if you can.